Method of and apparatus for concentrating liquid products



I Aug. 10, 1943. r HQALL 2,326,142

METHOD OF AND APPARATUS FOR CONCENTRATING LIQUID PRODUCTS Filed Feb. 7,1940 2 Sheets-Sheet l INVENTOR.

fisg viz M17012 ATTORNEYS.

Aug. 10, 1943.

J. M. HALL 2,326,142

. METHOD OF AND APPARATUS FOR CONCENTRATING LIQUID PRODUCTS 2Sheets-Sheet 2 J95 =15 w E 92 57 Q 2 1] 6] r L :Z:\\ [1 63" :r. 7 19 l(514 H 5 63 6] INVENTOR. -I052 6Q 55 7 g] 62 BYM/ ATTORNEYS.

atented Aug. 10, 1943 METHOD OF AND APPARATUS FOR CON- CENTRA ATINGLIQUID PRODUCTS Joseph M. Hall, Chicago, Ill., assignor to Drying &Concentrating Company, a corporation of Delaware Application February'7, 1940, Serial No. 317,722

11 Claims.

This invention relates to a system for concentrating liquid products orfor reducing the moisture content thereof.

One of the objects of the invention is the provision of a new andimproved method of concentrating liquid products with a minimum of heatloss.

Another object of the invention is the provision of a new and improvedmethod of :concentrating a liquid product by the use of air or other gasas'the heating medium arranged in a plurality of closed circuits.

A further object of the invention is the provision of a new and improvedapparatus for concentrating a liquid product that is provided with anovel arrangement of mechanism for circulating the drying or evaporatingmedium.

Another object of the invention is the provision of a new and improvedsystem for evaporating or condensing liquid products in a plurality ofstages by the use of air or other gas as the heating medium and. byemploying a single heating unit for the entire system.

Another object of the invention is the provision of a new and improvedmethod of concentrating a liquid product in such a manner that theentire process from the time the particles are introduced into any oneof the evaporators of the system until these same particles aredischarged therefrom requires but a few seconds of time. usually about aminute or so, whereby the treatment does not cause chemical changes in athe constituent particles of the product.

A still further object of the invention is the provision of anew andimproved apparatus for concentrating a liquid product that is simple inconstruction. easily assembled, efllcient in operation, and that may becleaned with a minimum of time and labor.

Other and further objects and advantages of the invention will appearfrom the following description, taken in connection with theaccompanying drawings, in which Fig. 1 is a side elevationpf the forwardend portion of the apparatus shown moreor less dia-. grammatically, withparts in section and parts broken away; A 3 Fig. la is a side elevationof the rear portion (f the apparatus shown more or lessdiagrammatically, with parts in section and parts broken Fig. 2 is aplan view of a portion of the concentrator chamber of the first stage ofevaporation;

Fig. 3 is a bottom plan view of the lower portion oi the first stageevaporator, shown diagrammatically;

Fig. 4 is a vertical section of the spray head and associatedstructure', with parts broken away; and

Fig. 5 is a section on the line 5-5 of Fig. 4.

It is common practice, in apparatuses having a plurality of stages of eaporation, to provide an evaporating chamber for each stage having meansfor operating one or more of the evap0- rato"s at sub-atmosphericpressure. Such a system is objectionable because of the additional powerrequired in operating the vacuum pumps and because, in a vacuum system,leaks that develop in the system lower the efficiency of the system verymaterially.

The present invention seeks to avoid these difficulties by the provisionof a system that operates at comparatively low temperatures and atsubstantially atmospheric pressure and, consequently, the equipment isvery much simplified. Where the vacuum system is employed, the apparatusmust be more strongly built to withstand the pressure of the atmosphere.But, in the present system, since there is but a comparatively smalldifference in the outside and inside pressures, the structure need notbe so heavy nor s0 massive.

In a system employing vacuum pans 0r chambers where heat is appliedindirectly, as in the previously named constructions, the liquid productmust necessarily be p1 esent in large quantities in the evaporators orvacuum pans in order to operate with any degree of efiiciency. But thisprolonged'exposure of the product to such temperatures as are necessaryto evaporate the liquid is objectionable as adversely affecting thequality of the product.

The present invention avoids this objection by employing a system inwhich the product is sprayed into direct contact with the heating mediumin small particles which are exposed to this medium for extremely shortperiods of time. Under ordinary operating conditions, the exposure inany one of the evaporators requires a comparatively few seconds of time,hence there is little time for any chemical change in the product duringthe concentrating period. This is considered an important feature ofthis invention. Milk, for instance, that has been concentrated in thismanner, will retain its original taste and flavor and may be returned toits original condition simply by adding the required amount of moistureto restore its original fluidity. The heating medium employed is agaseous fluid and for the purpose of disclosing one form of theinvention, air is used as the heat conveying medium.

Referring now to the drawings, the reference character l designates theconcentrating system which comprises a first stage concentrator orevaporator II, a second stage concentrator or evaporator l2, a thirdstage concentrator or evaporator l3, and a fan 4 for circulating theheating medium through the first closed circuit. This circuit includesthe fan l4, a heater l5, the evaporator II, a condenser or heatexchanger l6, and connecting conduits. The system also includes a secondclosed circuit for the drying medium comprising a fan means H, thecondenser or heat exchanger i6, for heating the heating medium in thissecond circuit, a condenser l8, and the connecting conduits. In thethird stage concentrating mechanism, air from the outside is drawn intothe system through the condenser or heat exchanger 18 for heating thesame. This air is caused, by the fan I9, to pass through the third stageconcentrator or evaporator l3 and is discharged into the air. The liquidproduct is contained in the receptacle or container 2|and is conductedto the evaporators or concentrators in series,

that is, in regular order fromthe first, throughthe second, to the thirdconcentrator and sprayed therein, respectively, as will presentlyappear.

Each concentrating stage has a separate circulating system for theheating medium and the condenser for the air circuit of the firstv stagefunctions as a heater for the second stage air circuit. Likewise, thecondenser for the second stage air circuit functions as a heater for thethird stage air circuit. 1

The apparatus for effecting the first stage evaporation will now bedescribed.

Starting with the air discharged from the fa [4, the same will passalong the conduit- 22 into and through the heater IS. The fan I4 is ofthe usual centrifugal type and need not be described in detail. Theheater l5 may be of the usual or any well known type, that shown beingof flue or tubular type and mounted in the upper portion of a furnace23. The furnace 23 comprises a combustion chamber 24,

a heating chamber 25 located above the compear.

The rear wall 33 of the furnace is provided with an opening 34 intowhich the rear end of a conduit 4| is secured. The conduit 32 is abranch of the conduit 4|, as clearly shown in Fig. 1.

The heating chamber 25 is provided with flue sheets or partitions 35 and36 at the forward and rear ends of the heating' chamber within which arerigidly secured a plurality of parallel flues or tubes 31 through whichthe air from the fan l4 travels during the operation of the apparatus.combustion chamber 24 pass upwardly through the passages 38 in the topwall 21 of the combustion chamber and flow about the front ends of thetubes 31 and then downwardly on the The heated gases from the oppositeside of a baille 39 around the rear ends of the tubes 31 and into thesmoke chamber 26 for heating the air as it passes through the tubes.Since the burner 29 is of the usual or any well known construction, itis not thought necessary to further illustrate or describe the same.

Suitable means are provided for returning a portion of the combustiongases to thecombustion chamber to be recirculated through the heater ISin order to conserve the heat contained therein. As shown, the passage32 is employed for this purpose. The passage 32 is connected to a mainpassage 4| secured in the opening 34 and has its front end secured inthe opening 3|. In order to control the amount of combustion gasesrecirculated through the passage 32, a valve 42 is provided for closingeither the passage 4| or the passage 32 or partially closing either, asmay be desired. The heated air from the heater l5 passes through aconduit 43 into a snail 44 mounted on the concentrator chamber II andpasses into that chamber through a passage 45 in a downwardly spiralmovement.

The concentrator II is of the centrifugal type and comprises an uppercylindrical section 46, a lower tapered section 41 and a top wall 48which may be-depressed as at 49 and is joined to a sleeve 99 for formingthe axial passage 45. The

snail 44 is'connected to the top wall 48 by the sleeve portion 99 whichdefines the opening 45. Extending downwardly through the snail 44 is acasing or sleeve 5|, the lower end of which exwithin which is rotatablymounted a shaft ml or passage 96 for collecting th liquid which will bemoving spirally when it flows into the channel. An outlet passage 91 isprovided which is'arranged tangent to the channel 96, as shown in Fig.3, whereby the liquid flowing in the direction of the arrow in saidfigure will readily flow into the passag 91. This liquid flows into areservoir 38 from which it is drawn by the pump NH and discharged intothe second stag concentrator l2.

The distributor member 56 comprises a hollow body portion 51 incommunication with the axial bore of the tubular member 55. Suitablearms 6|, having bores 62 in communication with the hollow head 51, aresecured in th head and ex- I tend radially outwardly therefrom. Anysuitable number of these arms may be employed, four being shown. Thebores 62 are reduced very materially in diameter at the outer nds of thearms to form nozzles 63 which may, in practice, be

detachable so that nozzles of different bores may be employed for use inconcentrating fluids of different viscosities. When the liquid productis fed to the head, the same will be discharged through the bore 62 andnozzles 63 by centrifugal force for atomizing the product.

Suitable means are provided for deflecting the air across the nozzles.This means comprises an annular deflector member 64 in the form of thefrustum of a cone having an outer concave face, as shown at 65. Thisdeflector is supported by the arms BI and rotates with them. The air, inbeing discharged from the snail 44 will be deflected outwardly acrossthe nozzles into direct contact with the finely divided particlesdischarged by the nozzles 63 and being in intimate contact with thoseparticles will evaporate a considerable portion of the moisture fromthem in the concentrator. The annular recess 90 formed by the centraldepression in the top wall of the concentrating chamber II issufficiently above the sprayed liquid that none of the spray collects onthis wall.

Suitable means are provided for rotating the distributor head 56 andarms and deflector rigidly connected thereto. As shown, a motor 66,

mounted on the enlargement 52, is provided for this purpose. The shaft55 may be a continuatlon of the motor shaft or may be rigidly attachedthereto.

Appropriate means are provided for exhausting the air from theconcentrator I I. As shown, the arms 6| of the distributor head 56 arefiattened and turned at an angle so that they will function as anexhaustfan for removing the air from the concentrator II. The rotationof the distributor member performs the double 1 function of atoinizingthe liquid product and of exhausting the air from the dehydratingchamber.

The liquid product is forced, by a pump IIII, through a passage 61 fromthe container 2| downwardly through the hollow motor shaft 55. Thisliquid passes outwardly by the action of centrifugal force through therotating nozzles and is discharged therefrom in the form of a spray,that is, the particles are finely divided or are atomized. The air, asit enters the evaporator II, is caused to rotate at a high velocity bythe snail 44" and, moving across thenozzles 63. will evaporate aconsiderable portion of the moisture fromv the particles and thecentrifugal force will throw the particles outwardly into the spirallymoving air thus evaporating moisture from the solid material. The airwill move downwardly in a spiral until it'reaches the lower end of theevaporator II and then will be caused to move upwardly in a spiral ofcomparatively small diameter by the fan formed by the arms SI and willbe discharged into the heat exchanger I6 by the passage 53. The liquidparticles will be thrown by centrifugal force outwardly against the sidewall of the concentrator and will be caused to flow in a spiral path bythe spirally moving air current down the side wall into. the channel 96.

In the heat exchanger I6, the vapor in the air is condensed and aconsiderable portion of 6 its sensible and latent heat is transferred tothe air in the circuit of the second evaporator stage, as will presentlyappear. The heat-exchanger I6 is of the usual or any well known type andcomprises a casing 40 having'a'flue sheet or partition 50 at one end anda similar flue or partition 60 at its opposite end within which aresecured the ends of tubes III as clearly shown in Fig. 1 of thedrawings. The air passing through the conduit or passage 53 enters theside of the casing 40 adjacent the partition 50, flows about or aroundthe tubes I and is discharged through a conduit 80 at its opposite end.The conduit 80 constitutes the intake of the fan I4 thus completing thecircuit for the air through the first stage evaporation.

The drying medium, which, in the present instance, is air, is alsocirculated in a closed cir cuit in the second evaporating stage. Thesecond stage evaporating mechanism comprises an evaporator I2, and spraymember or atomizing mechanism 68 which is similar to the spray member 56described above. The evaporator I2 is similar in construction to theevaporator II and has mounted thereon a snail 69' similar to the snail44 previously described. The snail 69 is in communication with the fanIT by a conduit 'II through which air discharged from said fan passesinto the evaporator I2 in adownwardly moving spiral as has already beendescribed.

A sleeve 12, depending from the casing 13, extends axially downwardlyinto the evaporator I2 and has mounted axially therein a sleeve I4within which is the rotating motor shaft of the motor I6 for rotatingthe spray head 68. Since the construction of the evaporator I2, sprayhead 68 and the arrangement of the snail 69, sleeves I2 and 14 aresubstantially the same as in the construction described above, it is notthought necessary to repeat the description of these parts at this time.

The air withdrawn by the fan formed by the arms of the,distributormember 68 is discharged through a conduit 11 into a heat exchanger I8The heat exchanger I8 comprises a casing 18 having a flue sheet orpartition 19 at one end and a flue sheet or partition 8I at the oppositeend. Flues or tubes 82 are secured at their ends in the partitions as isusual in such constructions. Saturated air from the conduit 1'! passesinto the casing I8 and flows downwardly about the tubes 82 and isdischarged into a conduit 83 which is in communication with the casing40. From the conduit 83, the air passes upwardly through the tubes ID ofthe heat exchanger I6 into the fan I! and from the fan I! through theconduit II into. the evaporator chamber I2. From the chamber I2 andconduit TI, this air passes through the heat exchanger I8thus'completing the closed circuit of the heating medium for the secondstage evaporator I2. The air, as it passes upwardly through the tubes orflues I8, is heated by conduction from the air'of the first stagecircuit as'the latter flows downwardly through the heat exchanger IE.This upwardly flowing air cools the air flowing downwardly from theconduit 53 thus condensing a considerable amount of the moisture whichis discharged from the casing through a pipe 84. The air in the secondevaporating stage circulates in a closed circuit and consequently, themoisture evapo rated from the liquid product in the evaporator I2 mustbe removed in order that the mechanism shall properly function.

The heat exchanger I8 is provided for this purpose. At its upper end,this exchanger is provided with a tubular extension 85 through whichfresh air is caused to flow by the fan I9. This moisture contained inthe air flowing through the closed circuit in the second stageevaporator. The

moisture condensed from this air in the heat the temperature withinthose chambers.

exchanger I8 may escape through an outlet pipe 81 in the lower portionof the casing 18. Preferably, though not necessarily, a filter 88 isprovided in the tubular extension 85. The tubular extension 85 mayextend to the exterior of the building in which the mechanism is locatedand in that event, a protecting cap 89 is provided for preventing ,theentrance of rain, snow and the like, into said extension. The fresh airintroduced into the heat exchanger I8 passes downwardly through thetubes 82 of the heat exchanger I8 where it is heated and in return,cools the air in the second stage evaporating circuit. It then passesinto the fan I 9 and is there discharged into the third stage evaporatorI3 and from thence into the air, thereby constituting what may be termedthe air circuit for the third stage evaporator.

The mechanism for the third stage evaporating circuit comprises theevaporator I3 and associated parts and since it is similar to thatalready described, it is not thought necessary to further illustrate ordescribe the same.

The air discharged from the third stage evaporator I3 by the fan I9 ordistributor member I09 is forced upwardly through the sleeve or tubularmember 9| and is discharged into the atmosphere through a pipe orpassage 92 which may extend to the exterior of the building and beprovided with a protective cap 93.

Thermometers 94 may be placed anterior and posterior to the heater l andto each of the evaporators and heat exchangers for indicating thetemperature of the air flowing through the different systems.Thermometers 94 may also be mounted on the evaporator chambers toindicate The distribution of the liquid product and as sociatedmechanism will now be described. The product is contained in thereceptacle 2| and is delivered by a pump I I0 to the distributor member56. The liquid product is atomized and the particles are thrown bycentrifugal force, as described above, against the walls of the firstevaporator chamber and'flow downwardly therein into the circular channel96 in a circular movement and are discharged through the tangentialpassage 91 into the reservoir 98 and from there pumped through theconduit I02 by the pump IM to the distributor member as. The liquid isfurther concentrated in the concentrator I2 and is collected in thechannel I03 which is similar to the channel 96 in the first stageevaporator. The concentrate that collects in the channel I03 is movingclockwise in the channel and escapes from the channel through a conduitI 04 arranged tangentially to the channel I03 in a manner similar tothat already described. The concentrate is collected in a reservoir I05from which it ispumped by the pump I06 into the third stage evaporatorI3 where it is still further concentrated and is discharged into thereservoir I01 in its final concentrated form.

Certain liquid products are impaired and their chief characteristicsvery much afiected by high temperatures employed in the evaporatingstages. In the present invention, this is avoided by atomizing theproduct and discharging it in currents of air at moderately hightemperatures for only an extremely brief interval of time. It has beenfound that treated under such conditions, the products, such as milk;for instance, will retain all the original flavor and othercharacteristics.

Suitable valves I20 are provided for the reservoirs 98, I05 and I01 forremoving the concentrate therefrom, if desired.

While in the construction shown, mechanism for a three stage evaporatingsystem only is disclosed, it is evident that any suitable number ofadditional closed evaporating stages or circuits similar to the secondstage circuit mechanism may be added between the second and third stageevaporating mechanism. It is also understood that the second stage maybe omitted, if desired, for reducing the number of evaporating stages.

The system, as shown, may be regarded as composed of a front, a rear,and an intermediate section. The front section comprises the heater I5,fan I4 and. first stage evaporator II; the intermediate sectioncomprises the second stage evaporator mechanism including the heatexchanger IB, the fan I1 and evaporator I2; and, the rear sectionincludes the heat exchanger I8, the fan I9 and the third stageevaporator I3. The system may be contracted by removing the intermediatesection which may be done by disconnecting the conduits 22, 53 and I02at the points H2, H3 and H4 between the front and intermediate sectionsand at the points H5, H6 and H1 in the conduits 83, I1 and I00 betweenthe rear and intermediate sections, closing the valve I I8 in the liquidconduit I04, and then connecting the conduits 83 and 11 of the rearsection to the corresponding conduits 22 and 53 of the front section.Additional intermediate units may be added between the forward andintermediate units or between the intermediate units or between twointermediate units. In other words, the intermediate units areinterchangeable. This is considered an important feature of theinvention because it permits the system to be enlarged or contracted tomeet different operatin'g conditions.

If a larger number of stages of evaporation be employed, in theinterests of economy, the initial temperatures used should be increasedto the point where the air and product discharged from the system arebut slightly above atmospheric temperature.

In all constructions, the heat exchangers in the system function as acondenser for the preceding closed circuit and also as a heater for thesucceeding circuit. The system is flexible it can be extended orcontracted, as desired, and be operated at various temperatures as bestadapted for the particular product to be treated.

With the use of the centrifugal type of evaporator chamber for eachstage of evaporation, the highest temperature for'the drying medium maybe relatively low, as for concentrating milk, for instance, and may bein the neighborhood of boiling water. This is extremely important in theevaporation or concentration of certain products, especially thoseproducts that are affected by chemical reactions caused or acceleratedby high temperatures.

7 The following is one example of how the system may be operated inconcentrating milk. Air enters the first stage evaporator II at around219' F. and leaves the same at around F. approximately saturated. Anumber of heat units are removed in the condenser from this saturatedair thus condensing the moisture therefrom. These heat units aretransferred to the air circuit of the second stage evaporator forheating the air in that circuit. The number of heat units removed by theheat exchanger Hi from the air in the first stage evaporator circuit arereplaced by the heater I5. Likewise, the number of heat units removed inthe second stage evaporator circuit by the heat exchanger I 8 andtransferred to the air entering the third stage evaporator are replacedby the heat units transferred to it by the heat exchanger 16. The numberof heat units transferred from the first evaporator circuit to thesecond, in the example given, and from the second to the third in theoperation of thesystem may be the same in all stages. In each circuit,the air leaves the evaporator'chamber substantially saturated. Thetemperature of the air entering each evaporator chamber is decreas ingorder. For instance, air enters the second evaporator 12 at around 166F. and leaves at around 125 F. saturated and the airenters the thirdchamber at around 115 E. and leaves at 73 F. saturated. The liquidproduct enters the first chamber at around 80 F., the second at around175 F. and the third around 125 F. and leaves the third around 73 F. Thesystem may be operated differently for difierent products and underdifferent conditions and the above is given as one example of how thesystem may be operated in the interests of economy.

The construction herein disclosed has a high degree of efiiciencybecause of the intimate contact between the air and the fine particlesof the sprayed product at each stage of evaporation. Because of thisefliciencyin evaporation of the product in each stage, the air in thefirst stage need not necessarily be above about 220 F. when it entersthe first stage evaporator.- This temperature will not adversely affectthe evaporation of milk. The system may be operated at highertemperatures, if desired, for evaporating other products or even milk ifa greater degree of concentration is desired. But, if materially highertemperatures are employed, for instance, an addition unit may benecessary in the interest of economy, in this respect, the saturated airdischarged from the system should be about, or possibly above, thetemperature of the outside air.

It will thus be seen that there are three circuits for the dryingmedium; that the first two are closed circuit, and the third an opencircuit; that there is a circuit for each evaporating stage; that thedrying medium for the first stage only is heated; that the-dryingmediums for the remaining stages are heated by a heat exchanger from thepreceding stage; and, that the drying mediums operate at moderatetemperature.

It is thought from the foregoing, taken in connection with theaccompanying drawings, that the construction and operation of my devicewill be apparent'to those skilled in the art and that changes in size,shape, proportion and detail may be made without departing from thespirit and scope of the appended claims.

I claim as my invention: i

1. A method ofconcentrating a liquid product which comprises dischargingthe product in the form of a spray into a spirally moving current ofheated air for evaporating a portion of the moisture of said product toform a concentrate, transferring a portion of the heat of said heatedair to another volume of air, causing the last-named air to movespirally into a second stage evaporator chamber, spraying saidconcentrate into said last-named spirally moving air, and removing theconcentrate from said second-stage evaporator.

2. A system for concentrating liquid products comprising a plurality ofconcentrating stages, a centrifugal evaporator in each stage, means forgaseous drying medium for each stage, means for causing said medium tocirculate through said evaporators for evaporating moisture from thesprayed particles, means for heating the drying medium in the firststage evaporator, and means for transferring heat from the first stagemedium in succession to the mediums of the remaining stages.forevaporating moisture from the sprayed concentrate from the precedingevaporating stage.

3. In a system for dehydrating a liquid product, a first stage section,a final stage section and one or more intermediate stage sections, eachstage section comprising a cyclone separator type of concentrator, andhaving a separate circuit for a heating medium for each section and acommon heat exchange! between adjacent sections, means-for addingthermal units to the heating medium of the first stage section, means,including said heat exchangers, for transferring y. portion of thoseunits to the remaining stage sections successively, means for causingthe heating medium in the chambers to move spirally, and means forspraying the product into the spirally moving air in each chamber, inseries,

from the first to the final stage sections.

4. In a system for dehydrating a liquid product, a first stage section,a final stage section and one or more intermediate stage sections,

each stage section comprising a cyclone separator type of-concentratorand having a separate gaseous drying medium circuit for each stagesection, means for adding thermal units to the drying-medium of thefront stage section, heat exchangers common to adjacent sections fortransferring heat from the drying medium of the first stage section tothe drying medium of the other stage sections in succession, means fordischarging the liquid product into said air within said chambers, meansfor conducting the air from the top portions of the chambers, and meansfor conducting the concentrate from the lower portions of said chambers.

5. An apparatus for concentrating liquid products comprising first,second and third stage evaporators, a first stage heat exchanger and asecond stage heat exchanger, means for circulating a drying mediumthrough said first stage evaporator and first stage heat exchanger in aclosed circuit, means for heating the drying medium just prior to itsentry into the first stage evaporator, means for circulating a dryingmedium through said second stage evaporator and through said first andsecond stage heat exchangers in a closed circuit, means for circulatingfresh air through the third stage evaporator and said second stage heatexchanger, means for spraying a liquid product into the first stageevaporator for concentrating the product, means for spraying theconcentrate from the first stage evaporator into the second stageevaporator for further concentrating said product, and means forspraying the further concentrated product spraying a liquid product ineach evaporator, a

from said second stage evaporator into said third stage evaporator fordehydrating the same.

chamber, except the last, to the spraying means of the succeedingchamber,a heater anterior to the first evaporating chamber, a .heatexchanger anterior to. each of the remaining evaporating chambers andposterior to each, except the last, conduits for "conducting a gaseousdrying medium exchangers,'conduits for forming a closed circuit for adrying medium through each of the succeeding chambersandcorresponding-heat' exchangers in a closed circuit,'except forthelast to and from the firstchamber in a closed circuit through saidheater'and the first of. said heat evaporator chamber, the drying mediumfor which is discharged directly into the air,, and means in eachchambe'r-forcausing the drying medium to descend-man outer spiral and toascend to the discharge opening in an inner said evaporators in" seriesin the order named, a

heater, a first and a second stage heat exchanger,

means for continuously cir'culating'a drying medium through said heater,first stage evaporator a closed circuit for removingjmoisture from saidand through said first stage heat exchanger in product, means forcirculating a drying medium through said first stage heat exchanger,said second stage exaporator and through said second stage heatexchanger in a closed circuit for removing further moisturefrom saidproduct, and

means for circulating a drying medium through er between theintermediate and final stage evaporators, means for circulating a dryingmedium through said heater, first stage evaporatorand the firstmentioned heat exchanger, means for circulating a separate body ofdrying medium through said first-named heat exchanger, said intermediatestage evaporator and said second heat exchanger, means for circulating abody of air through said second heat exchanger and said final stageevaporator, and means for detachably connecting said sections together,said means being so constructed and arranged that said in'termediatemechanism may be removed and said first and final stage mechanisms maybe operatively connectedtogether.

10. In a system for concentrating liquid products, an apparatuscomprising a first stage section, a final stage section and at least oneintermediate'stages'ection, each section comprising a cyclone separatortype of evaporator chamber and each section having a separate aircircuit, a heat exchanger common to adjacent sections,

. means for forcing air through each of said circuits and through thecorrespondingheati'exchanger, said heat exchangers constitutingcondensers for the preceding circuit and a heater for the nextsucceeding circuit, means for spraying a liquid product in successioninto said sections into the air moving through said evaporators, andmeans for detachabiy connecting said sections together whereby thenumber of sections said second stage heat exchanger and said third,

stage evaporator for removing still further moisture from said product,said heat exchangers functioning as condensers for the one circuit andas a heater for the following circuit.

8. A method of concentrating a liquid product which comprisesevaporating moisture from the product in a plurality of stages in seriesby first r spraying the product into a current of spirally I moving airconfined in a chamber in each stagein succession, causing the air in thefirst stage chamber to fiow in-a closed circuit through a heater, thenthrough said last-named chamber for removing moisture from said productand then through a heat exchanger for removing moisture from said air,causing air for the second stage chamber to how through said heatexchanger for heating said air, then through said second stage chamberfor removing further moistime from said product, then through a secondheat exchanger, and finally causing fresh air to flow through saidlast-named heat exchanger through the-last-stage chamber and into theatmosphere.

9. In a system for concentrating a liquid product, a first tageevaporating mechanism, a final stage evaporating mechanism and aremovable intermediate stage evaporating mechanism arranged in series,means for spraying a liquid product into said evaporators in series,each mechanism comprising a cyclone type of evapo rator, a heater forthe first stage evaporator, a heat exchanger between the first andintermediate stage mechanisms, a second heat exchangmay be readilyexpanded or contracted.

11. In an apparatus for evaporating moisture from a liquid-product, aplurality of evaporating chambers of the centrifugal type arranged in'series for the-passage of the product there- ,through, a reservoir for,containing the liquid product'to be evaporated, liquid spraying means ineach chamber for, spraying said product into a rotating body ofgaseousmedium in said chamber, means for conducting said product from saidreservoir: to the spraying means in the first chamber of said series andfor conducting the concentrated product from said first chamber to thespraying means of .the succeeding chamber, a heater anterior to thefirst evaporating chamber and a heat exchanger posterior thereof,conduits for conducting a gaseous drying medium to and -from the firstchamber, means including said through said heat conduits and a fanforcirculating all of said drying medium through said heater in a spiralpath through the first chamber of said series and then exchanger in aclosed circuit, in the order named, conduits for conducting a gaseouevaporating medium through said heat exchanger for heating saidevaporating medium and for causing the removal of moisture bycondensation from the gaseous drying medium flowing through said heatexchanger, and means including said last-named conduits and a fan forcausing all of said evaporating medium to flow through said heatexchanger and the next adjacent evaporator chamber of said series in theorder named for further reducing the moisture contentof said liquidproduct.

JOSEPH M. HALL.

